Cardiac pacemakers for treating bradycardia commonly employ pacing leads for connecting an electrical pulse generator to excitable cardiac tissue, usually within the heart's right ventricle. Such leads have one or more electrodes proximate the distal end thereof and also commonly employ tines located just distal of the tip electrode for holding that electrode in contact with endocardial tissue in the right ventricle. The tines engage the trabeculae, resisting movement of the lead tip due to body movement and/or contractions of the heart muscle itself.
More recently, researchers have found that cardiac stimulation can have a beneficial effect in treating patients suffering from congestive heart failure (CHF). By properly controlling the AV interval of the pacemaker, a sick heart may be made to pump more efficiently. Pacing therapy for the treatment of CHF, however, often requires the ability to stimulate the left ventricle, either alone or in conjunction with right ventricular stimulation. Current methods for achieving left ventricular pacing require placement of an epicardial lead, via thoracotomy or a thoracoscopic approach. Because of the usual poor condition of CHF patients, both of these procedures are "high risk" due to the trauma of the surgery itself and the need for general anesthesia. To obviate the need for a thoracotomy, left ventricular access (LVA) leads have been developed that may be introduced through the coronary sinus and then advanced through the coronary veins so that the lead's stimulating tip electrode can be positioned on the surface of the left ventricle near the apex of the heart.
It is sometimes difficult to feed an endocardial or intravenous lead along the desired predetermined path to implant the electrode or electrodes in a desired implantation site, either in a chamber of the heart or in a selected coronary vein. This is especially true for routing leads through the coronary sinus and into a branching vein on the left myocardium. The difficulties often are a result of anomalies in the vascular anatomy and the number of veins encountered when locating the desired path. Furthermore, controlling the LVA lead's movement is difficult because of the long tubular structure of a lead and its corresponding stylet/guide wire. The stylet/guide wire has to be rigid enough to afford pushability to the lead and provide navigation of the lead so as to arrive at the desired location. In addition, there must be enough torque control so that by twisting the lead at its proximal end, torque will then be transmitted along the lead to its distal end. However, existing devices do not allow the physician to selectively torque only the stylet or only the lead or both when positioning the lead. Thus, a need exists to have a torque device which allows independent torquing of the lead and stylet along with the ability to torque the stylet and lead together.